Effects of cognitive training under hypoxia on cognitive proficiency and neuroplasticity in remitted patients with mood disorders and healthy individuals: ALTIBRAIN study protocol for a randomized controlled trial.

BACKGROUND: Cognitive impairment is prevalent across neuropsychiatric disorders but there is a lack of treatment strategies with robust, enduring effects. Emerging evidence indicates that altitude-like hypoxia cognition training may induce long-lasting neuroplasticity and improve cognition. We will investigate whether repeated cognition training under normobaric hypoxia can improve cognitive functions in healthy individuals and patients with affective disorders and the neurobiological underpinnings of such effects. METHODS: In sub-study 1, 120 healthy participants are randomized to one of four treatment arms in a double-blind manner, allowing for examination of separate and combined effects of three-week repeated moderate hypoxia and cognitive training, respectively. In sub-study 2, 60 remitted patients with major depressive disorder or bipolar disorder are randomized to hypoxia with cognition training or treatment as usual. Assessments of cognition, psychosocial functioning, and quality of life are performed at baseline, end-of-treatment, and at 1-month follow-up. Functional magnetic resonance imaging (fMRI) scans are conducted at baseline and 1-month follow-up, and [11C]UCB-J positron emission tomography (PET) scans are performed at end-of-treatment to quantify the synaptic vesicle glycoprotein 2A (SV2A). The primary outcome is a cognitive composite score of attention, verbal memory, and executive functions. Statistical power of ≥ 80% is reached to detect a clinically relevant between-group difference with minimum n = 26 per treatment arm. Behavioral data are analyzed with an intention-to-treat approach using mixed models. fMRI data is analyzed with the FMRIB Software Library, while PET data is quantified using the simplified reference tissue model (SRTM) with centrum semiovale as reference region. DISCUSSION: The results will provide novel insights into whether repeated hypoxia cognition training increases cognition and brain plasticity, which can aid future treatment development strategies. TRIAL REGISTRATION: ClinicalTrials.gov, NCT06121206 . Registered on 31 October 2023.

Effect of high-flow nasal cannula oxygen versus standard oxygen on mortality in patients with acute hypoxaemic respiratory failure: protocol for a multicentre, randomised controlled trial (SOHO).

INTRODUCTION: First-line oxygenation strategy in patients with acute hypoxaemic respiratory failure consists in standard oxygen or high-flow nasal oxygen therapy. Clinical practice guidelines suggest the use of high-flow nasal oxygen rather than standard oxygen. However, findings remain contradictory with a low level of certainty. We hypothesise that compared with standard oxygen, high-flow nasal oxygen may reduce mortality in patients with acute hypoxaemic respiratory failure. METHOD AND ANALYSIS: The Standard Oxygen versus High-flow nasal Oxygen-trial is an investigator-initiated, multicentre, open-label, randomised controlled trial comparing high-flow nasal oxygen versus standard oxygen in patients admitted to an intensive care unit (ICU) for acute respiratory failure with moderate-to-severe hypoxaemia. 1110 patients will be randomly assigned to one of the two groups with a ratio of 1:1. The primary outcome is the number of patients who died 28 days after randomisation. Secondary outcomes include comfort, dyspnoea and oxygenation 1 hour after treatment initiation, the number of patients intubated at day 28, mortality in ICU, in hospital and until day 90, and complications during ICU stay. ETHICS AND DISSEMINATION: The study has been approved by the central Ethics Committee 'Sud Méditerranée III' (2020-07-05) and patients will be included after informed consent. The results will be submitted for publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04468126.

Randomized crossover trial of a demand oxygen delivery system in nocturnal hypoxemia.

The newly developed portable oxygen concentrator with an auto-demand oxygen delivery system (auto-DODS) automatically switches between 3 sensitivities according to the negative pressure gradient of inhalation and supplies oxygen only during inhalation. The aim of this study was to verify the effectiveness and safety of auto-demand devices compared with a continuous flow oxygen concentrator, during sleep, in a randomized crossover noninferiority trial. We alternatively used an auto-DODS or a continuous-flow oxygen concentrator, all night on separate days for HOT (Home Oxygen Therapy) patients with nocturnal hypoxemic symptoms. The primary endpoints were the mean value of oxygen saturation (SpO2) over the total sleep time. The secondary endpoints included the efficacy endpoints and the safety endpoints. Regarding the primary endpoint, the difference in SpO2 between the auto-DODS and continuous flow was 0.835%. Since the upper limit of this difference did not exceed 2.8, which was set as the noninferiority margin, it was shown that the auto-DODS did not reduce SpO2 by at least 2.8% on average compared to continuous flow. No equipment failure or exacerbation of disease was observed, confirming the safety of the auto-DODS during the night.

Perioxygenation During Advanced Airway Management.

ABSTRACT: Advanced airway management is a skill that is used every day in patient care settings throughout the world. Albeit common, it is not benign. Advanced airway management may either be elective or urgent; in either case, it may result in significant patient morbiidity and mortality. The complications of difficult or failed endotracheal intubation can be severe and include death or permanent neurologic injury. Difficulty or failure with advanced airway management often coincides with the onset of hypoxia. The onset of hypoxia affects both the patient and the airway manager. While hypoxemia may result in dysrhythmias and ultimately cardiac arrest for the patient, it adds time pressure and stress to the airway manager, and thus may impact successful performance. In this review, we will discuss how to identify patients at risk for rapid desaturation during advanced airway management. Additionally, methods of peri-oxygenation throughout the performance of airway management will be discussed.

Long-Term Oxygen Therapy for 24 or 15 Hours per Day in Severe Hypoxemia.

BACKGROUND: Long-term oxygen supplementation for at least 15 hours per day prolongs survival among patients with severe hypoxemia. On the basis of a nonrandomized comparison, long-term oxygen therapy has been recommended to be used for 24 hours per day, a more burdensome regimen. METHODS: To test the hypothesis that long-term oxygen therapy used for 24 hours per day does not result in a lower risk of hospitalization or death at 1 year than therapy for 15 hours per day, we conducted a multicenter, registry-based, randomized, controlled trial involving patients who were starting oxygen therapy for chronic, severe hypoxemia at rest. The patients were randomly assigned to receive long-term oxygen therapy for 24 or 15 hours per day. The primary outcome, assessed in a time-to-event analysis, was a composite of hospitalization or death from any cause within 1 year. Secondary outcomes included the individual components of the primary outcome assessed at 3 and 12 months. RESULTS: Between May 18, 2018, and April 4, 2022, a total of 241 patients were randomly assigned to receive long-term oxygen therapy for 24 hours per day (117 patients) or 15 hours per day (124 patients). No patient was lost to follow-up. At 12 months, the median patient-reported daily duration of oxygen therapy was 24.0 hours (interquartile range, 21.0 to 24.0) in the 24-hour group and 15.0 hours (interquartile range, 15.0 to 16.0) in the 15-hour group. The risk of hospitalization or death within 1 year in the 24-hour group was not lower than that in the 15-hour group (mean rate, 124.7 and 124.5 events per 100 person-years, respectively; hazard ratio, 0.99; 95% confidence interval [CI], 0.72 to 1.36; 90% CI, 0.76 to 1.29; P = 0.007 for nonsuperiority). The groups did not differ substantially in the incidence of hospitalization for any cause, death from any cause, or adverse events. CONCLUSIONS: Among patients with severe hypoxemia, long-term oxygen therapy used for 24 hours per day did not result in a lower risk of hospitalization or death within 1 year than therapy for 15 hours per day. (Funded by the Crafoord Foundation and others; REDOX ClinicalTrials.gov number, NCT03441204.).

Noninvasive vs invasive respiratory support for patients with acute hypoxemic respiratory failure.

BACKGROUND: Noninvasive respiratory support modalities are common alternatives to mechanical ventilation in acute hypoxemic respiratory failure. However, studies historically compare noninvasive respiratory support to conventional oxygen rather than mechanical ventilation. In this study, we compared outcomes in patients with acute hypoxemic respiratory failure treated initially with noninvasive respiratory support to patients treated initially with invasive mechanical ventilation. METHODS: This is a retrospective observational cohort study between January 1, 2018 and December 31, 2019 at a large healthcare network in the United States. We used a validated phenotyping algorithm to classify adult patients (≥18 years) with eligible International Classification of Diseases codes into two cohorts: those treated initially with noninvasive respiratory support or those treated invasive mechanical ventilation only. The primary outcome was time-to-in-hospital death analyzed using an inverse probability of treatment weighted Cox model adjusted for potential confounders. Secondary outcomes included time-to-hospital discharge alive. A secondary analysis was conducted to examine potential differences between noninvasive positive pressure ventilation and nasal high flow. RESULTS: During the study period, 3177 patients met inclusion criteria (40% invasive mechanical ventilation, 60% noninvasive respiratory support). Initial noninvasive respiratory support was not associated with a decreased hazard of in-hospital death (HR: 0.65, 95% CI: 0.35-1.2), but was associated with an increased hazard of discharge alive (HR: 2.26, 95% CI: 1.92-2.67). In-hospital death varied between the nasal high flow (HR 3.27, 95% CI: 1.43-7.45) and noninvasive positive pressure ventilation (HR 0.52, 95% CI 0.25-1.07), but both were associated with increased likelihood of discharge alive (nasal high flow HR 2.12, 95 CI: 1.25-3.57; noninvasive positive pressure ventilation HR 2.29, 95% CI: 1.92-2.74). CONCLUSIONS: These data show that noninvasive respiratory support is not associated with reduced hazards of in-hospital death but is associated with hospital discharge alive.

Improving effective coverage of medical-oxygen services for neonates and children in health facilities in Uganda: a before-after intervention study.

BACKGROUND: Medical oxygen services are essential for the care of acutely unwell patients. We aimed to assess the effects of a multilevel, multicomponent health-system intervention on hypoxaemia detection, oxygen therapy, and mortality among neonates and children attending level IV health centres and hospitals in Uganda. METHODS: For this before-after intervention study, we included children who attended paediatric or neonatal wards of 24 level IV health centres and seven general or regional referral hospitals in the Busoga and North Buganda regions of Uganda between June 1, 2020, and June 30, 2022. All neonates younger than 1 month and children aged 1 month to 14 years were eligible for inclusion. We excluded neonates who were not sick but stayed in the maternity ward for routine postnatal care. The intervention involved clinical training, mentorship, and supportive supervision; provision of pulse oximeters and cylinder-based oxygen sources; biomedical-capacity support; and support to develop and disseminate oxygen supply strategies, oxygen therapy guidelines, and lists of essential oxygen supplies. Trained research assistants extracted individual patient data from case notes using a standardised electronic data collection form. Data were collected on health-facility details, age, sex, clinical signs and symptoms, admission diagnoses, pulse oximetry readings, oxygen therapy details, and final patient outcome. The primary outcome was the proportion of admitted neonates and children with a pulse oximetry oxygen saturation reading documented in their patient case notes on day 1 of health-facility admission (ie, pulse oximetry coverage). We used mixed-effects logistic regression to evaluate the effect of the intervention. FINDINGS: We obtained data on 71 997 eligible neonates and children admitted to 31 participating health facilities; the primary analysis included 10 001 patients in the pre-intervention period (ie, June 1 to Oct 30, 2020) and 51 329 patients in the post-intervention period (ie, March 1, 2021, to June 30, 2022). Because 1356 patients had missing data for sex, 4365 (46·7%) of 9347 in the pre-intervention group and 22 831 (46·2%) of 49 410 in the post-intervention group were female; 4982 (53·3%) in the pre-intervention group and 26 579 (53·8%) in the post-intervention group were male. The proportion of neonates and children with pulse oximetry at admission increased from 2365 (23·7%) of 10 001 in the pre-intervention period to 45 029 (87·7%) of 51 328 in the post-intervention period. Adjusted analysis indicated greater likelihood of a patient receiving pulse oximetry during the post-intervention period compared with the pre-intervention period (adjusted odds ratio 40·10, 95% CI 37·38-42·93; p<0·0001). INTERPRETATION: Large-scale improvements in hospital oxygen services are achievable and have the potential to improve clinical outcomes. Governments should be encouraged to develop national oxygen plans and focus investment on interventions that have been shown to be effective, including the introduction of pulse oximetry into routine hospital care and clinical and biomedical mentoring and support. FUNDING: Bill & Melinda Gates Foundation and ELMA Philanthropies. TRANSLATIONS: For the Luganda and Lusoga translations of the abstract see Supplementary Materials section.

2023 Year in Review: Home Oxygen Therapy.

Long-term oxygen therapy (LTOT) is a treatment that involves the provision of supplemental oxygen to individuals with respiratory disease to correct hypoxemia in the post-acute care environment. Over 1.5 million adults in the United States use supplemental oxygen for various respiratory disorders. This paper explores literature published on LTOT from September 2022-September 2023. Upon the conclusion of this literature review, 4 distinct categories emerged. This paper highlights the significant findings associated with the 4 categories: supplemental oxygen and COVID-19, telemonitoring, LTOT equipment, and in-home high-flow nasal cannula.

Digital Twins of Acute Hypoxemic Respiratory Failure Patients Suggest a Mechanistic Basis for Success and Failure of Noninvasive Ventilation.

OBJECTIVES: To clarify the mechanistic basis for the success or failure of noninvasive ventilation (NIV) in acute hypoxemic respiratory failure (AHRF). DESIGN: We created digital twins based on mechanistic computational models of individual patients with AHRF. SETTING: Interdisciplinary Collaboration in Systems Medicine Research Network. SUBJECTS: We used individual patient data from 30 moderate-to-severe AHRF patients who had failed high-flow nasal cannula (HFNC) therapy and subsequently underwent a trial of NIV. INTERVENTIONS: Using the digital twins, we evaluated lung mechanics, quantified the separate contributions of external support and patient respiratory effort to lung injury indices, and investigated their relative impact on NIV success or failure. MEASUREMENTS AND MAIN RESULTS: In digital twins of patients who successfully completed/failed NIV, after 2 hours of the trial the mean (sd) of the change in total lung stress was -10.9 (6.2)/-0.35 (3.38) cm H2O, mechanical power -13.4 (12.2)/-1.0 (5.4) J/min, and total lung strain 0.02 (0.24)/0.16 (0.30). In the digital twins, positive end-expiratory pressure (PEEP) produced by HFNC was similar to that set during NIV. In digital twins of patients who failed NIV vs. those who succeeded, intrinsic PEEP was 3.5 (0.6) vs. 2.3 (0.8) cm H2O, inspiratory pressure support was 8.3 (5.9) vs. 22.3 (7.2) cm H2O, and tidal volume was 10.9 (1.2) vs. 9.4 (1.8) mL/kg. In digital twins, successful NIV increased respiratory system compliance +25.0 (16.4) mL/cm H2O, lowered inspiratory muscle pressure -9.7 (9.6) cm H2O, and reduced the contribution of patient spontaneous breathing to total driving pressure by 57.0%. CONCLUSIONS: In digital twins of AHRF patients, successful NIV improved lung mechanics, lowering respiratory effort and indices associated with lung injury. NIV failed in patients for whom only low levels of positive inspiratory pressure support could be applied without risking patient self-inflicted lung injury due to excessive tidal volumes.

Efficacy of high-flow nasal oxygen therapy started in the emergency room versus conventional oxygen therapy in patients with acute hypoxaemic respiratory distress: protocol for a French multicentric, prospective, open and randomised superiority study protocol (HIFLOWED).

INTRODUCTION: Acute respiratory failure is a life-threatening condition frequently found in the emergency department. High-flow nasal oxygen (HFNO) is increasingly used in emergency departments for patients with hypoxaemic acute respiratory failure. However, despite the increasing number of studies, its potential advantages regarding the need for therapeutic escalation and mortality have not been precisely evaluated. Our objective is to compare conventional oxygen therapy to HFNO when they are initiated during the first hour following the patient's arrival at the emergency department, with the hypothesis that HFNO would reduce the need for ventilatory therapy escalation. METHODS AND ANALYSIS: This is a multicentric, prospective, open and randomised superiority study. 500 inpatients will be randomised (1:1) to receive conventional oxygen therapy or HNFO. The primary outcome is a failure in the oxygen therapy defined as the need for a therapeutic escalation within 4 hours after therapy initiation. ETHICS AND DISSEMINATION: The study has been submitted and approved by the Comité de Protection des Personnes Nord Ouest IV (20 October 2020). As required, a notification was sent to the Agence nationale de sécurité du médicament et des produits de santé (22 October 2020). The research results will be published in peer-reviewed publications and presented at international conferences. TRIAL REGISTRATION NUMBER: NCT04607967.

Thoracic Society of Australia and New Zealand clinical practice guideline on adult home oxygen therapy.

This Thoracic Society of Australia and New Zealand Guideline on the provision of home oxygen therapy in adults updates a previous Guideline from 2015. The Guideline is based upon a systematic review and meta-analysis of literature to September 2022 and the strength of recommendations is based on GRADE methodology. Long-term oxygen therapy (LTOT) is recommended for its mortality benefit for patients with COPD and other chronic respiratory diseases who have consistent evidence of significant hypoxaemia at rest (PaO2 ≤ 55 mm Hg or PaO2 ≤59 mm Hg in the presence of hypoxaemic sequalae) while in a stable state. Evidence does not support the use of LTOT for patients with COPD who have moderate hypoxaemia or isolated nocturnal hypoxaemia. In the absence of hypoxaemia, there is no evidence that oxygen provides greater palliation of breathlessness than air. Evidence does not support the use of supplemental oxygen therapy during pulmonary rehabilitation in those with COPD and exertional desaturation but normal resting arterial blood gases. Both positive and negative effects of LTOT have been described, including on quality of life. Education about how and when to use oxygen therapy in order to maximize its benefits, including the use of different delivery devices, expectations and limitations of therapy and information about hazards and risks associated with its use are key when embarking upon this treatment.

Mechanical chest compressions as a last-ditch attempt to salvage a profoundly hypoxic but normotensive patient with a massive pulmonary embolism.

Massive pulmonary embolism is a common cause of morbidity and mortality. For patients presenting with massive pulmonary embolism, severe hypoxia is usually associated with severe hypotension. These patients should be considered for thrombectomy should thrombolysis and respiratory support fail to improve their condition. Should thrombectomy not be available or suitable, consideration should be given to offering mechanical chest compressions to 'break up the clot'. We describe a case in which this seemingly led to survival and full recovery.

Respiratory support with standard low-flow oxygen therapy, high-flow oxygen therapy or continuous positive airway pressure in adults with acute hypoxaemic respiratory failure in a resource-limited setting: protocol for a randomised, open-label, clinical trial - the Acute Respiratory Intervention StudiEs in Africa (ARISE-AFRICA) study.

RATIONALE: Acute hypoxaemic respiratory failure (AHRF) is associated with high mortality in sub-Saharan Africa. This is at least in part due to critical care-related resource constraints including limited access to invasive mechanical ventilation and/or highly skilled acute care workers. Continuous positive airway pressure (CPAP) and high-flow oxygen by nasal cannula (HFNC) may prove useful to reduce intubation, and therefore, improve survival outcomes among critically ill patients, particularly in resource-limited settings, but data in such settings are lacking. The aim of this study is to determine whether CPAP or HFNC as compared with standard oxygen therapy, could reduce mortality among adults presenting with AHRF in a resource-limited setting. METHODS: This is a prospective, multicentre, randomised, controlled, stepped wedge trial, in which patients presenting with AHRF in Uganda will be randomly assigned to standard oxygen therapy delivered through a face mask, HFNC oxygen or CPAP. The primary outcome is all-cause mortality at 28 days. Secondary outcomes include the number of patients with criteria for intubation at day 7, the number of patients intubated at day 28, ventilator-free days at day 28 and tolerance of each respiratory support. ETHICS AND DISSEMINATION: The study has obtained ethical approval from the Research and Ethics Committee, School of Biomedical Sciences, College of Health Sciences, Makerere University as well as the Uganda National Council for Science and Technology. Patients will be included after informed consent. The results will be submitted for publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04693403. PROTOCOL VERSION: 8 September 2023; version 5.

Chronic obstructive pulmonary disease and obstructive sleep apnea overlap: who to treat and how?

INTRODUCTION: The co-existence of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA), or the overlap syndrome, is common and associated with a distinct pattern of nocturnal hypoxemia and worse clinical outcomes than either disease alone. Consequently, identifying who and how to treat these patients is essential. AREAS COVERED: Treatment is recommended in all patients with OSA and symptoms or systemic hypertension, but determining symptoms attributable to OSA can be challenging in patients with COPD. Treatment should be considered in asymptomatic patients with moderate to severe OSA and COPD with pulmonary hypertension and comorbid cardiovascular and cerebrovascular disease, especially if marked hypoxic burden. CPAP is effective, but in patients with the overlap syndrome and daytime hypercapnia, high-intensity noninvasive ventilation aiming to lower PaCO2 may have additional benefits. Additionally, in those with severe resting daytime hypoxemia, supplemental oxygen improves survival and should be added to positive airway pressure. The role of alternative non-positive airway pressure therapies in the overlap syndrome needs further study. EXPERT OPINION: Both COPD and OSA are heterogeneous disorders with a wide range of disease severity and further research is needed to better characterize and prognosticate patients with the overlap syndrome to personalize treatment.

Feasibility of Delivering 5-Day Normobaric Hypoxia Breathing in a Hospital Setting.

BACKGROUND: Beneficial effects of breathing at [Formula: see text] < 0.21 on disease outcomes have been reported in previous preclinical and clinical studies. However, the safety and intra-hospital feasibility of breathing hypoxic gas for 5 d have not been established. In this study, we examined the physiologic effects of breathing a gas mixture with [Formula: see text] as low as 0.11 in 5 healthy volunteers. METHODS: All 5 subjects completed the study, spending 5 consecutive days in a hypoxic tent, where the ambient oxygen level was lowered in a stepwise manner over 5 d, from [Formula: see text] of 0.16 on the first day to [Formula: see text] of 0.11 on the fifth day of the study. All the subjects returned to an environment at room air on the sixth day. The subjects' [Formula: see text], heart rate, and breathing frequency were continuously recorded, along with daily blood sampling, neurologic evaluations, transthoracic echocardiography, and mental status assessments. RESULTS: Breathing hypoxia concentration dependently caused profound physiologic changes, including decreased [Formula: see text] and increased heart rate. At [Formula: see text] of 0.14, the mean [Formula: see text] was 92%; at [Formula: see text] of 0.13, the mean [Formula: see text] was 93%; at [Formula: see text] of 0.12, the mean [Formula: see text] was 88%; at [Formula: see text] of 0.11, the mean [Formula: see text] was 85%; and, finally, at an [Formula: see text] of 0.21, the mean [Formula: see text] was 98%. These changes were accompanied by increased erythropoietin levels and reticulocyte counts in blood. All 5 subjects concluded the study with no adverse events. No subjects exhibited signs of mental status changes or pulmonary hypertension. CONCLUSIONS: Results of the current physiologic study suggests that, within a hospital setting, delivering [Formula: see text] as low as 0.11 is feasible and safe in healthy subjects, and provides the foundation for future studies in which therapeutic effects of hypoxia breathing are tested.

Noninvasive ventilation on reintubation in patients with obesity and hypoxemic respiratory failure following abdominal surgery: a post hoc analysis of a randomized clinical trial.

PURPOSE: Although noninvasive ventilation (NIV) may reduce reintubation in patients with acute hypoxemic respiratory failure following abdominal surgery, this strategy has not been specifically assessed in patients with obesity. METHODS: We conducted a post hoc analysis of a multicenter randomized controlled trial comparing NIV delivered via facial mask to standard oxygen therapy among patients with obesity and acute hypoxemic respiratory failure within 7 days after abdominal surgery. The primary outcome was reintubation within 7 days. Secondary outcomes were invasive ventilation-free days at day 30, intensive care unit (ICU)-acquired pneumonia and 30-day survival. RESULTS: Among 293 patients with hypoxemic respiratory failure following abdominal surgery, 76 (26%) patients had obesity and were included in the intention-to-treat analysis. Reintubation rate was significantly lower with NIV (13/42, 31%) than with standard oxygen therapy (19/34, 56%) within 7 days (absolute difference: - 25%, 95% confidence interval (CI) - 49 to - 1%, p = 0.03). NIV was associated with significantly more invasive ventilation-free days compared with standard oxygen therapy (27.1 ± 8.6 vs 22.7 ± 11.1 days; p = 0.02), while fewer patients developed ICU-acquired pneumonia (1/42, 2% vs 6/34, 18%; p = 0.04). The 30-day survival was 98% in the NIV group (41/42) versus 85% in the standard oxygen therapy (p = 0.08). In patients with body mass index (BMI) < 30 kg/m2, no significant difference was observed between NIV (36/105, 34%) and standard oxygen therapy (47/109, 43%, p = 0.03). An interaction test showed no statistically significant difference between the two subsets (BMI ≥ 30 kg/m2 and BMI < 30 kg/m2). CONCLUSIONS: Among patients with obesity and hypoxemic respiratory failure following abdominal surgery, use of NIV compared with standard oxygen therapy reduced the risk of reintubation within 7 days, contrary to patients without obesity. However, no interaction was found according to the presence of obesity or not, suggesting either a lack of power to conclude in the non-obese subgroup despite existing differences, or that the statistical difference found in the overall sample was driven by a large effect in the obese subsets.